Field of the Invention
The present invention relates to a die casting machine which injects and fills a mold with a molten metal supplied into an injection sleeve by advancing of an injection plunger, and a control method of the die casting machine.
Description of the Related Art
In a general die casting machine conventionally used, a metal material molten in a melting furnace is measured and scooped with a ladle for each shot, scooped molten metal is supplied to a supply port of an injection sleeve, and the molten metal is injected into and fills a cavity of a mold by an advance movement of an injection plunger provided inside the injection sleeve so as to be capable of advancing and retracting, so as to perform forming of a cast molded object.
An injection step of the die casting machine which injects the molten metal into the cavity of the mold includes a low-speed injection step and a high-speed injection step subsequent thereto. In the high-speed injection step, it is necessary to inject and fill the mold with the molten metal, at an injection speed of a high speed by one order of magnitude faster than an injection speed of an injection molding machine molding plastic products. Therefore, in the injection step, as a drive source for injecting and filling the cavity of the mold with the molten metal by the advance movement of the injection plunger, an electric servomotor is adopted as the drive source in the low-speed injection step, and on the other hand, a high-speed injecting and filling of the mold is performed in the high-speed injection step, by a hydraulic pressure drive source or by adding driving forces of the hydraulic pressure drive source and the electric servomotor, since larger driving force is necessary. As ones related to such technique, for example, JP-A-2008-73708 (Patent Document 1) discloses a control method of a die casting machine, which advances an injection plunger using an electric servomotor as a drive source in a low-speed injection step, and advances the injection plunger by a cooperation of drive sources of the hydraulic pressure drive source and the electric servomotor in a high-speed injection step.
However, in the conventional technique disclosed in Patent Document 1, the injecting and filling is performed by advancing the plunger rod by coordinating a hydraulic pressure control mechanism operated by a hydraulic pressure source and an advance-retract control mechanism using an electric servomotor as a drive source, in the high-speed injection step in which the operation is performed at extreme high speed. As such, in the high-speed injection step operated with the hydraulic pressure source having larger driving force than the electric servomotor as a main drive source, there were cases where the operation of the advance-retract control mechanism using the electric servomotor as the drive source cannot follow the operation of the hydraulic pressure control mechanism operated by the hydraulic pressure source, which makes it difficult to perform coordinate operation control, and also leads to a breaking of the advance-retract control mechanism.